A variety of approaches have been taken over the years to prevent a vehicle having an automatic transmission from creeping when in a stopped condition with the transmission in neutral with the engine running and to provide a smooth start-up from a stopped or virtually stopped condition.
A system that employs a mechanism for raising the idling speed of the engine during warm-up and also for automatically disengaging or partially disengaging the clutch when the brakes are applied at the lowest speed is described in U.S. Pat. No. 4,105,101, the disclosure of which is incorporated herein by reference.
A somewhat similar concept is disclosed in U.S. Pat. No. 4,194,608, of which the disclosure is incorporated herein by reference, teaches a means by which to adjust throttle position when the clutch assembly uncouples the transmission from the engine.
U.S Pat. No. 4,513,638, the disclosure of which is incorporated herein by reference, discloses a system that prevents the clutch from coupling the transmission to the engine when the throttle valve is in idle and the gear shift is moved from neutral to another position.
A system for reducing torque applied to an automatic transmission when the engine is idling is disclosed in
U.S. Pat. No. 4,514,811, the disclosure of which is incorporated herein by reference.
Other examples of systems for controlling creep and/or enhancing smoothness in start-up of vehicles having automatic transmissions are disclosed in U.S. Pat. Nos. 4,579,202; 4,618,043; 4,4698,763; 4,711,141; and 4,714,144, the disclosures of all of which are incorporated herein by reference.
Although the control systems disclosed in the above-described references may have their particular advantages, they characteristically employ means for automatically disengaging or partially engaging the clutch often in combination with some type of fuel control to maintain a desired idling speed and, although the previously described mechanism in U.S. Pat. No. 4,105,101 utilizes partial disengagement of the vehicle brakes as a smoothing function, such is done only in conjunction with idle speed control and does not include the advantage of partial clutch engagement.